This feature allows a returned missionary to opt to share their contact information with former mission leaders (mission president and mission president companion). It does not provide any capability that allows a returned missionary to see information about other missionaries.
The option to opt in to share contact information is only enabled for missionaries who began serving in January 2000 or later. When the feature is enabled, you will see an option in Member Tools settings and in Church Account settings that lists your former mission leaders and an option to share contact information with them.